Conventionally, a vehicle driving system is known which includes an internal combustion engine, an electric motor, a first engaging and disengaging means and a second engaging and disengaging means (for example, refer to Patent Document 1).
As shown in FIG. 10, a vehicle driving system 200 of Patent Document 1 is a dual-clutch transmission which includes a first input shaft 202a that is connected to an electric motor 210 and which is selectively connected to an internal combustion engine output shaft 204 by a first engaging and disengaging means 205, a second input shaft 202b that is selectively connected to the internal combustion engine output shaft 204 by a second engaging and disengaging means 206, an output shaft 203 that outputs power to a driven portion, a first gearset that is disposed on the first input shaft 202a and which includes plural gears that are selectively connected to the first input shaft 202a via first synchronizing units 230, 231, a second gearsets that is disposed on the second input shaft 202b and which includes plural gears that are selectively connected to the second input shaft 202b via second synchronizing units 216, 217, and a third gearset that is disposed on the output shaft 203 and which includes plural gears that mesh with the gears of the first gearset and the gears of the second gearset.